In MA plumbing code, is there something called the "barrel test" for shower interior?

Hi, I have tried to Google "barrel test" and "shower", and not finding anything to back up this salesperson's statement.

I live in MA, which I think is under the UPC. I'm trying to see if my idea for a shower is valid under the code. I am a homeowner and not a plumber. I have an existing 36 inch by 32 inch space that I would like to fit a shower into (for various reasons).

I checked the code at mass.gov, and it says "900 square inches" for the shower interior.
That implies (to me) that an allowable interior is 30 inches by 30 inches (= 900 sq. inches), and allowing 2 inches for curbing, that a 32 inch by 32 inch pan would be allowable under the code.

However, I was in a bath supply shop and the salesperson told me that the minimum allowable was 36 inch by 36 inch by MA state plumbing code. She said they have the "barrel test" and try to fit a barrel into the shower.

So, I guess I have these questions:
- Has anyone heard of something called the "barrel test" with respect to the UPC or MA plumbing code? Is it the same as this salesperson said?

- Does the UPC allow a minimum shower interior of 30 inch by 30 inch, or must it be 36 in. by 36 in.?

UPC 411.7 says the shower compartment shall have a minimum finshed interior dimension of 1024 square inches AND shall be capable of encompassing a 30" diameter circle. That would be your "barrel" test.

A 32 x 32 pan would not pass, because the finished interior dimension would be less than 32 X 32, and the second requirement prohibits building a very long but narrow shower.

Hi, thanks for confirming that the salesperson wasn't crazy talking about a "barrel test". She was very helpful otherwise, and I didn't want to disbelieve her on everything because I couldn't verify this barrel test thing.

jadnashua, thanks for the suggestion to talk to the local inspector. I can do that. He's been helpful in the past when I've called with questions, though he always seems reluctant to speak directly to the homeowner. In the past, he's said in so many words "have you hired the plumber yet?" and I have to explain that I just want to know if something I have in my head would be "dead in the water" code-wise before I have to pay my architect to see about putting it into the plan. I'm definitely not planning on doing my own plumbing! If it's not going to be to code, then I will just do without the shower and put a cabinet in there.

jimbo, I appreciate your comments. I don't feel that you are "busting my chops"--I have absolutely no *inkling* of doing any such work myself. No scintilla of that thought at all! It is the furthest from my mind.

I do want the job to be to code, and I got burned in the past by a MA licensed, well-known-in-the-community, recommended plumber doing something contrary to the code. So, "once bitten, twice shy"--this time I want to find out as much as possible what's allowed so that I can "trust, but verify" when the plumbers tell me what they'd do.

Thanks also for posting the link to the MA state code. I was incorrect--it seems to be titled "Uniform State Plumbing Code", and I confused it with "UPC". The MA citation reads a little more complicated than the UPC--so I'll ask the local inspector to clarify. At least now I can ask him a very specific question about the dimensions and why I'm asking.